Adolescent drug use is a complex problem with multiple determinants. Risk for drug use initiation, escalation, and problem use is increased by exposure to characteristics across socialization domains involving the family, school, community, and peer groups. The prevention of juvenile drug use and its complex facets requires comprehensive community interventions, that is, multicomponent interventions that work in concert across domains to reduce risk. The Communities That Care strategy employs community mobilization processes to reduce risk factors and increase protective factors against drug abuse. Mobilization consists of four phases: (1) community key leader recruitment and orientation; (2) community advisory board formation; (3) risk and resource assessment by the community board to identify priority risk factors; and (4) action planning and implementation of empircally-based family, school, and community interventions to reduce risk factors and enhance protective factors, with an emphasis on developmental appropriateness. Design recommendations are offered for evaluating the Communities that Care strategy and other comprehensive community interventions. These recommendations concern community selection, matching communities, information sources for matching, randomization, analysis unit, selecting the number of communities, intervention targets, measurement design, and testing the effectiveness of individual intervention components. An appendix contains information on drug abuse risk factors. 24 references, 3 notes, and 1 table